1. The effects of soil composition on the
decomposition rates of buried mice.
Aslin Fanning
Senior
Southern Illinois University Edwardsville

2. Taphonomy
• Taphonomy is the study of the processes of decay
(Forbes cited in Tibbett M and Carter DO (editors)
2008, p 205-216). Physical anthropologists can use
information on the rate of decay for many
applications.
• Little research has been conducted on how burial
in soil effects these processes.
• This experiment aimed to determine how soil
composition effects taphonomy in burial settings.

3. Soil Composition
• Soils are classified in taxonomic levels just like organisms.
There are twelve main soil orders and each of these
orders have suborders ([NRCS, USDA] 2003).
• Two of the three soil orders that can be found in Illinois
are located near Southern Illinois University Edwardsville.
The experimental conditions for this experiment were
obtained from Eldon Hazlet State Park in Carlyle, IL.
• The experimental conditions belong to the Alfisol and
Entisol family and are commonly called Bluford Silt Loam
and Wakeland Silt Loam.
• The soil composition is the only variable that will
influence the carcasses. To ensure this, the soils were
sterilized to remove all microorganisms.

4. Alfisol Entisol
Bluford Silt Loam Wakeland Silt Loam

5. Mice As Animal Models
• Hairless rodents, like mice, can be used in these studies when
pigs and other larger hairless animals are not suitable
(Petersen 2003).
• Mice are the best-suited models for this particular study. The
mice were received already euthanized and frozen. The were
purchased from RodentPro.com and did not require IRB
approval for use.
• Mice are more cost efficient, require less space and
decompose faster than larger organisms. It is ethically
responsible to use the smallest possible organisms when an
experiment requires the death of that organism, especially in
preliminary studies like this one.
• The time constraints of this experiment were limited to one
academic semester.

6. Setup and Preparation
• Carcasses were housed in specially
designed wooden viewing containers with
plexiglass bottoms for viewing.
• The top and bottom compartments
separate to allow for photographs and
observations.
• Container 1 housed specimen A. The
carcass was covered by the Alfisol sample,
Bluford Silt Loam.
• Container 2 housed specimen B. The
carcass was covered by the Entisol sample,
Wakeland Silt Loam.
• Container 3 served as the control and
remained uncovered with soil.
• There was also a container 4 (not pictured)
that contained only the subsoil and no top
portion or carcass. All containers were held
in a temperature controlled environment
that remained at approximately 68°F with
no insect activity possible.

7. Soil Chemistry and
Decomposition
• As an organism decays the cells break down and liquefy
(Byers 2008). As these bodily fluids leach into the subsoil, they
change the chemistry of the underlying soil. A good way to
measure changes in soil chemistry is by measuring the pH
levels.
• The measurement of changes in acidity can signal different
stages of decay (Stokes and others cited in Ritz and others
(editors) 2009, p 360-374).
• Experiments conducted on the effects of decomposing
carcasses on the underlying subsoil suggested that nitrogen
and phosphorus levels could also be good indicators of the
level of decomposition of the carcass lying above.
• They measured nitrogen and phosphorus in addition to
measuring the pH levels (Stokes and others cited in Ritz and
others (editors) 2009, p 360-374).

8. Observations
• In addition to the measurement of chemical changes in
the sub-soil, the experiment also utilizes visual
observations.
• The containers were designed to allow the researcher to
view and photograph the buried carcasses throughout
the entire experiment.
• Since burial research in taphonomic studies needs
further exploration, the ability to watch the entire
decomposition process as it occurs beneath soil is a
unique component to the experiment.
• These descriptions were used to place the carcasses into
five stages of decomposition: fresh, early decay, active
decay, skeletonization and advanced skeletonization
(Galloway et al 1989). I further split the early decay
category into two separate categories based on the
presence of bloating.

9. Methods
Visual Data pH
• Initial appearance of each • The pH levels of the subsoil
mouse was documented in this experiment was
prior to burial and carcass measured using pH test
photographed. strips.
• Each carcass was viewed • The testing solution was
and photographed daily acquired from a 50/50
and any changes to the mixture of soil and distilled
carcasses were noted. water that mixed for 1 week
• Carcasses were classified was shaken for 30 seconds
into stages (Galloway et al and filtered for testing.
1989) and then scored to • The pH levels were recorded
track differences between initially, and then every
specimen. Monday, Wednesday, and
Friday for the remainder of
the experiment.

10. Methods
Nitrogen Phosphorous
• Levels of both NO2 and • Phosphorus was also
NO3 were recorded in measured using the same
ppm using the same solution as the pH and
solution as the pH. nitrogen.
• The nitrogen levels were • The phosphorus levels
recorded at the start of were recorded initially,
the experiment, then on then every Monday,
every Monday, Wednesday, any Friday
Wednesday, any Friday for the remainder of the
for the remainder of the experiment.
experiment.
*The testing of these variables was ceased after the fourth week.

11. Initial Burial 1/25/13
Specimen A Specimen B Specimen C
Alfisol Entisol Control

12. Week 1 2/1/13
Specimen A Specimen B Specimen C
Alfisol Entisol Control

13. Week 2 2/8/13
Specimen A Specimen B Specimen C
Alfisol Entisol Control

14. Week 3 2/15/13
Specimen A Specimen B Specimen C
Alfisol Entisol Control

15. Week 4 2/22/13
Specimen A Specimen B Specimen C
Alfisol Entisol Control

16. Week 5 3/1/13
Specimen A Specimen B Specimen C
Alfisol Entisol Control

17. Week 6 3/8/13
Specimen A Specimen B Specimen C
Alfisol Entisol Control

18. Results
• The results of the experiment are inconclusive as to determine
the precise effects of the soil on decomposition rates.
• From the variables analyzed, it is not possible to determine if
the two experimental conditions used caused significant
changes in the rate of decomposition.
• The testing of nitrogen and phosphorus levels was ceased
after week 4. The data that was being recorded indicated
problems with the testing methods and not the effects of the
experimental conditions.
• Prior to the beginning of the experiment it was presumed that
water testing kits would be sufficient to test these variables but
the results indicate that the testing kits used, were insufficient
for these purposes.
• The carcasses decomposed in a similar manner to carcasses
in arid environments and the stages are recorded based on
those observations.
• Visual observations were also complicated by the unexpected
effects of the containers on the carcasses.
• The Alfisol sample had semi-obstructed views from day 28 on,
potentially complicating the score assessments.

19. Post-Experiment Analysis
Visual Data
Specimen A Specimen B Specimen C
Alfisol Entisol Control
• Fresh decay • Fresh Decay • Fresh Decay
lasted days 1-4. lasted days 1-2. lasted days 1-2.
• Early Decay (a) • Early Decay (a) • Early Decay (a)
lasted days 5-11. lasted days 3-11. lasted days 3-7.
• Early Decay (b) • Early Decay (b)
• Early Decay (b) lasted days 12- lasted days 8-18.
lasted days 12- 38. • Advanced
43. • Advanced Decay lasted
• Decomposition Decay lasted days 19-43.
score of 99. days 39-43. • Decomposition
• Decomposition score of 125.
score of 101.

20. pH Results

21. Nitrogen Results

22. Phosphorous Results

23. Decomposition Score
Decomposition Score
Stage Description Score
Fresh Fresh, no discoloration 1
Early Decay (a) lighter discoloration and presence of bloating 2
Early Decay (b) darker discoloration and absence of bloating 3
beginning of desiccation and appearance of bone
Advanced Decay on less that 50% of body 4
Bone visible on more than half of body and
Skeletonization desiccated tissue on less than 50% of body 5
Advanced Skeletonization Skeletonization with bleaching to bone 6
(Galloway et al 1989)

24. Discussion 1/2
• The results of this experiment proved to be inconclusive
due to all of the unforeseen factors that were
encountered.
• The results of this experiment proved that further
exploration into the effects of soil composition on
decomposition still need to be explored using different
methods and testing methods that directly test the soil.
• There was a slight difference in the decomposition score
of the Alfisol and Entisol specimens but it is possible that
due to the burial conditions of specimen A, the stage
indicators went unseen in the Alfisol covered specimen.
• The initial goal of the experiment may not have been
satisfied but the experiment yielded several options for
potential research opportunities.

25. Discussion 2/2
• The containers in which the carcasses were housed were
unique to this project. Further research with enclosures
like these, is required to understand the effects they
have on burial decomposition.
• All of the carcasses in the experiment, including the
control, behaved in unexpected manners for the
environment of the St. Louis area.
• The carcass reacted as if they were housed in an arid
environment. This may be due to the season of testing.
• The results of this experiment open up research ideas for
further exploration on the effects of containers and soil
sterilization on buried carcasses.
• It is also possible that the size of the animal was the
cause of the observed behaviors and further research
on the size of carcass on decomposition rates would be
another useful area of exploration in burial settings.

26. Acknowledgements
• Special recognition goes to Everett Clark for the funding
of this experiment. And to my family for all their love and
support.
• Thanks are also given to Bryan Fitch from the Marion, IL
USDA-NRCS office for his help and advisement in
locating the soil samples.
• Credits additionally go to the very dedicated professors
of the SIUE Anthropology Department, especially Dr.
Rehg who was the primary advisor for this research and
my mentor during my time at Southern Illinois University
Edwardsville.
• I would also like to thank Southern Illinois University
Edwardsville for giving me the opportunity to conduct
this research.

27. References Cited
• Byers S. 2008. Introduction to Forensic Anthropology. Boston, MA. Pearson
Publishing. p. 110-119.
• Carter DO, Tibbett M. 2008. Cadaver Decomposition and Soil: Processes.
Tibbett M, Carter DO (editors). In Soil Analysis in Forensic Taphonomy:
Chemical and Biological Effects of Buried Human Remains. CRC: Press. p. 31-
44.
• Forbes SL. 2008. Decomposition Chemistry in a Burial Environment. Tibbett M,
Carter DO (editors). In Soil Analysis in Forensic Taphonomy: Chemical and
Biological Effects of Buried Human Remains. CRC: Press. p. 205-216.
• Galloway A, Birkby WA, Jones AM, Henry TE, Parks, BO. 1989. Decay Rates of
human remains in an arid environment. Journal of Forensic Sciences 34:607-
616.
• [NRCS, USDA] Soil Survey Staff. 2003. Keys to Soil Taxonomy. 9th ed.
Washington D.C.: USDA, NRCS. p. 37-41.
• Petersen AB. 2003. Sunless skin tanning with dihydroxyacetone delays broad-
spectrum ultraviolet photocarcinogenesis in hairless mice. Mutation Research
542(1-2):129-38.
• Stokes KL, Forbes SL, Benninger LA, Tibbett M and Carter DO. 2009.
Decomposition Studies Using Animal Models in Contrasting Environments:
Evidence From Temporal Changes in Soil Chemistry and Microbial Activity. Ritz
K, Dawson L, and Miller D (editors). Cited in Criminal and Environmental Soil
Forensics. Springer Publishing. p. 360-374.